diff --git a/app/models/cancerpredictfields.rb b/app/models/cancerpredictfields.rb
index e1e5a93..b4cfd57 100644
--- a/app/models/cancerpredictfields.rb
+++ b/app/models/cancerpredictfields.rb
@@ -308,7 +308,7 @@ class Cancerpredictfields
     js_code += "\n        #{self.tmp_hidden_variables_for_js}"
     formula = text_to_math(self.prediction_formula)
     self.all_variables.each do |k|
-      formula = formula.gsub(/#{k}?(-|\+|\*|\s|\=)/){ "result[\"#{k.strip}\"]#{$1}" }
+      formula = formula.gsub(/(\A|[^\w])#{k}($|[^\w])/){|f| "#{$1}result[\"#{k.strip}\"]#{$2}" }
     end
     formula_variables = self.tmp_lpv_variables.map{|v| v}
     js_code = "\n      function calculate_first_lpv(result_json){